Patent Document 1 describes a synchronous electric motor comprising a stator comprising a cylindrical magnetic core on which concyclic magnetic poles are provided with a conformal spacing, a non-ferrous metal collar for shading surrounding only one pole of these pairs of magnetic poles and a coil to be connected to a single phase AC source, and a rotor comprising an arbitrary number of turnable small permanent magnets made of sinter material small void away from the magnetic pole group of the stator.
FIG. 8 is a longitudinal section diagram of the synchronous electric motor of the Patent Document 1. In FIG. 8, when single phase AC is applied to the coil 2, the magnetic polarity of upper ends 5 and 6 of the cylindrical magnetic core 1 is sequentially moves. In this time, the small magnets 4 disposed on small shaft on the edge of a radial arm 3 of the rotor slightly turns according to the magnetic attraction and repulsion between nearest magnetic poles 5 and 6 on the stator side, and then starts to move to a predetermined direction prescribed by the rotor side fairly smoothly. After that, the small magnets 4 can connect rotation as long as current is applied to the coil 2. In other words, in the present motor, at the same time current is applied to a coil 3 at start, the small magnets 4 slightly turn around the small shaft and take the most appropriate position to receive rotational force, which constitutes an initiation. The small magnets 4 have a relationship as if the moon revolves around the earth.
Patent Document 2 describes a synchronous electric motor in which the rotor of a induction electric motor A and the rotor of a synchronous electric motor B are disposed on the same driving shaft, and the induction electric motor A mainly activates the driving shaft and continues rotation, and the synchronous electric motor B is powered by an output of a constant frequency of a vacuum tube circuit and compensates the driving shaft to rotate at a constant speed. In the synchronous electric motor B, the rotor is magnetized in such a manner that the same poles appear on the all periphery face or pole face facing the magnetic poles of a stator side, exciting coils are respectively wound around the magnetic poles of the stator side alternately in different wound direction and are connected to predetermined frequency power sources in series, and another magnetic passes reach to the rotor from yokes of the stator side are divided by nonmagnetic bodies.
FIG. 9 is a partial longitudinal section diagram showing the internal constitution of the synchronous electric motor of the Patent Document 2. In FIG. 9, the rotor of the synchronous electric motor B is entirely North pole or South pole on all around face, also a yoke is divided into internal and external two parts, 8 and 9, and the magnetic pass resistance between them is set at a very high adjustable value. Therefore, at start, under a very low resistance, the small induction electric motor A is good enough, and also to reach a speed close to a predetermined rotational speed, the motor never receives strong resistance from an electric generation operation.
In short, according to the invention, by the small inductive electric motor A, the driving shaft 7 at near (+) (−) of a predetermined rotation speed defined by the frequency of the output obtained from the vacuum tube circuit is started easily and entered into a normal rotation state. Also, only a compensation operation to maintain the driving shaft 7 at a predetermined rotation speed should be controlled by the synchronous electric motor B by the output obtained from the vacuum tube circuit. Consequently, electricity required for the electric motor B may be small, and the whole apparatus can be designed very easily and manufactured at a lower cost.
As just described, the synchronous electric motor of the invention of the Patent Document 1 comprises the stator comprises the coil to be connected with the single phase AC power supply and the rotor comprises small permanent magnets.
The synchronous electric motor of the Patent Document 2 comprises the general format inductive electric motor A comprises the stator includes the exciting coils receive commercial AC and a basket-shaped rotor, the synchronous electric motor B comprises the stator includes exciting coils a˜h and the magnetized rotor made of a hard paste material.
In either constitution, a stator is disposed concentrically covering the permanent magnets of a rotor, and rotation force is obtained by applying current to an exciting coil and generating a rotation magnetic field. To obtain this rotation force, sufficiently-large amounts of current are required, for obtaining a required torque. Also, to dispose a stator and rotor concentrically, it is required to maintain the gap between the stator and rotor with accuracy, and advanced design and production technologies are required.    [Patent Document 1] Japanese Examined Patent Publication No. 33-5011    [Patent Document 2] Japanese Examined Patent Publication No. 33-1961